This research has two major thrusts. (1) One is to follow a large sample of youngsters as they go through their 10th, 11th, and 12th years of schooling, the middle years of adolescence. These youngsters, who comprise a stratified random sample of Baltimore students, have already been continuously followed over their first nine years of school. Information has been secured directly from them, their parents and their teachers starting from the time they began first grade. (2) The other thrust is to analyze the information about these youngsters that is so far available in order to shed light on how their cognitive and affective development responds to social structural factors (minority/majority status, gender, family configuration, socioeconomic background, school SES and racial mix) and to their immediate social context (parents, teachers, peers). The general analytic strategy employs structural equation models to elucidate the processes by which the various social factors affect development. Considerable analysis of cognitive development is already available (see papers appended). Particular attention in future analyses would be paid to (a) the interdependence between cognitive and affective development; (b) how children negotiate transitions into middle school or school change more generally; (c) how developmental processes of minority and majority youngsters differ; (d) the extent to which continuity or discontinuity characterizes the developmental trajectories of this sample of "typical" urban children; (e) how children develop an academic self-image and sense of control, and especially how school performance shapes these aspects of personal development. The theoretical context for this work derives from life course ideas, sociological research on status attainment, and cognitive themes of child development. Understanding the social factors that shape "normal" development is fundamental to providing environments in which all children can develop to their full potential. Encouraging full development in childhood and adolescence benefits both mental and physical health over the long run, and benefits families as well as children.